1. Field of the Invention
The present invention relates to a rod-shaped light guide operative to receive light at an end face and emit light at a predetermined emitting surface, and to an image reading device having a rod-shaped light guide built therein.
2. Description of the Related Art
Facsimile machines, copiers, and scanners have a built-in image reading device provided with a rod-shaped light guide for illuminating a document with a line light and with a lens array for condensing light reflected from the document onto a line image sensor.
In such an image reading device, a rod-shaped light guide is required to illuminate a document with an amount of light sufficient to read the document. To address this requirement, there is disclosed a technology whereby a rod-shaped light guide is loaded in a white light guide case such that the surface emitting light is exposed (see, for example, patent document No. 1). By loading a rod-shaped light guide in a light guide case, light that leaks from the surface other than the light emitting surface is reflected by the light guide case and returned to the interior of the rod-shaped light guide. Thereby, light loss is reduced and the amount of emitted light is increased accordingly. [[patent document No. 1] JP 2006-148501
By loading a rod-shaped light guide in a light guide case to efficiently use light that leaks from the rod-shaped light guide, the number of components is increased and the step of loading the rod-shaped light guide in the light guide case is required with the result that the cost is increased.